Waste heat steam generator

Abstract

A waste heat steam generator for a gas and steam turbine power plant is provided. The generator has economizer, evaporator and superheater heating surfaces which form a flow path and through which a flow medium flows. An overflow line branches off from the flow path and leads to injection valves arranged downstream at a flow side of a superheater heating surface in the flow path. The overflow line permits a brief power increase of a downstream steam turbine without resulting in an excessive loss in efficiency of the steam process. The brief power increase is permitted independently of the type of waste heat steam generator. The branch location of the overflow line is arranged upstream of an evaporator heating surface at the flow medium side and downstream of an economizer heating surface.

The invention claimed is: 
     
       1. A waste heat steam generator for a combined cycle power plant, comprising:
 a plurality of economizer heating surfaces, evaporator heating surfaces, and superheater heating surfaces that form a flow path through which a flow medium flows; and 
 an overflow line that branches off from the flow path and leads to an injection valve disposed in the flow path on a flow medium side downstream of the superheater heating surface, 
 wherein a branching-off point of the overflow line is disposed on the flow medium side upstream of an evaporator heating surface and downstream of an economizer heating surface, 
 wherein the branching-off point of the overflow line is disposed on the flow medium side downstream of a last economizer heating surface, and 
 wherein a throughflow valve for the flow medium is disposed on the flow medium side downstream of the branching-off point of the overflow line. 
 
     
     
       2. The waste heat steam generator as claimed in  claim 1 , wherein a throughflow measurement device for the flow medium is disposed downstream of the branching-off point of the overflow line. 
     
     
       3. A method for regulating a short-term power increase of a steam turbine having an upstream waste heat generator, comprising:
 forming a flow path by a plurality of economizer, evaporator and superheater heating surfaces of the waste heat generator through which a flow medium flows; 
 branching off the flow medium by an overflow line from the flow path on a flow medium side upstream of an evaporator heating surface and downstream of an economizer heating surface; and 
 injecting the flow medium into the flow path on the flow medium side downstream of a superheater heating surface, 
 wherein the flow medium is branched off on the flow medium side downstream of a last economizer heating surface, and 
 wherein a throughflow valve for the flow medium is disposed on the flow medium side downstream of a branching point of the overflow line for regulating a throughflow of the flow medium. 
 
     
     
       4. The method as claimed in  claim 3 , wherein a throughflow of the flow medium on the flow medium side is measured downstream of a branching-off point of the overflow line.